Two-signal broadcast



Oct. 16, 1934. c. F. JENKINS TWO-SIGNAL BROADCAST Original Filed Aug. 29, 1927 Patented Oct. 16, 1934 PATENT OFFICE TWO SIGNAL BRQAD CAST Charles Francis Jenkins, Washington, D. 0., assignor, by mesne assignments, to Radio Corporation of America, a corporation of Delaware Refiled for abandoned application Serial No.

216,296, August 29, 1927.

This application March 14, 1932, Serial No. 598,845

4 Claims.

This invention relates to apparatus and methods employed in the radio art, and has for its main object a method of broadcasting simultaneously both audio-frequency signals, and signals above audibility.

With these and other objects in view, the invention consists in a method of simultaneously modulating a radiated wave in accordance with one message only at audio frequency and in accordance with another message only at superaudible frequency, as hereinafter disclosed and particularly pointed out in the claims.

Referring to the drawing,

Figure 1 is a schematic wiring plan embodying the invention;

Figs. 2 and 3 are illustrative sections of a ribbon which may be employed therein;

In the drawing 1 is a microphone; 2 is an induction coil; 3 a microphone battery; 4 an electron tube; 5 a filament battery; 6 a plate battery; 7 an antenna coupling; 8 a light-sensitive cell having a dark resistance to take the place of a grid leak; 9 a lens, for focusing the light of the source 10 upon the cell 8. 11 are rollers which in rotation pass a ribbon 12 through the light beam. 13 is a pair of resistance rollers to keep a steady tension on the ribbon 12 (shown edge on) as it passes through the light beam.

This ribbon may be celluloid, for example, a standard motion picture film, and may have dark areas thereon (Fig. 2) which would interrupt the light in an order to indicate the letters of the alphabet of the International or the Morse code while running through the light beam, or the ribbon may have modulated values of light and dark (Fig. 3) representing speech or music, as it is recorded on the edge of motion picture film which reproduces both speech and pictures.

With the radio circuit oscillating it is quite obvious that speech can be broadcast in the usual manner through the microphone and coupling shown, or any other standard proper circuit.

It is also well understood that if the grid leak resistance light cell 8 is disturbed by the pulsations of light falling thereon, caused by the slow movement of the ribbon 12 through the light beam, the telegraph code would be heard also, and neither the speech nor the code could be heard as well as if the other was quiet.

But if the passage of the ribbon through the light beam is speeded up until the changes in the grid leak resistance occur at radio frequencies, that is, above audibility, then each will function without interfering with the other. The carrier wave may be interrupted or modulated, as desired, as long as it is above audibility.

That is, the broadcast Wave carries both (1) audible frequencies, and (2) interrupted radio frequencies, the interruptions being above audibility.

The audible frequencies can, at the receiving station, be detected and translated in the usual manner with head phones, and the radio interruptions of the wave by suitable devices which are made the subject of a separate application.

The practical attainment possible with this invention is, therefore, the broadcasting of two sets of signals, each interrupted or modulated at will, the one set of signals representing speech and the other code; or two speeches, or music and pictures, apparatus for which is the subject of numerous applications.

It is obvious that other circuits and other means than those shown in the drawing could be employed without departing from the object of this invention, namely, the transmission of two sets of legible signals on the same radio wave.

The present application is filed to take the place of an application filed by me July 21, 1924, Serial No. 727,273, and an application Serial No. 216,296, filed August 29, 1927. A suitable receiving system for use with the invention is disclosed in application Serial No. 216,295, filed August 29, 1927.

What is claimed is:

1. In radio apparatus, a radio wave propagating means, means for interrupting said radio wave at super-audible frequencies, the interruptions varying in accordance with a message to be transmitted to a distant receiving station, and means for impressing on the same radio wave an audio frequency modulation, whereby audio message'signals and other signals of greater fre quency than the said audio signals may be transmitted simultaneously on a single carrier Wave to said receiving station.

2. In radio apparatus, a radio wave propagating means, means for interrupting said radio wave at radio frequencies said interruption varying in accordance with the message to be transmitted to a distant receiving station, and means for impressing on the same radio wave a modulation at audio frequencies only, whereby audio signals and other signals of greater frequency than the said audio signals may be transmitted simultaneously on a single carrier wave to said receiving station.

3. In radio apparatus, a radio wave propagating means, and means for changing said radio wave at super-audible frequencies according to which comprises producing at super-audible group frequency successive super-audible waves,

the duration of said groups varying in accordance with a message to be transmitted to a distant receiving station, and modulating the waves in each group with another message, the latter modulation being eifected only at audible frequencies, and transmitting said waves to a distant receiving station.

CHARLES FRANCIS JENKINS. 

